Method and system for stent retention using an adhesive

ABSTRACT

The invention provides a method of manufacturing a system for treating a vascular condition. A catheter including an inflatable balloon is provided. A stent is positioned over the balloon. An adhesive material is applied between an inner surface of the stent and an outer surface of the balloon. The adhesive material is heated to above a melting point of the adhesive material. The adhesive material is cooled to below a melting point of the adhesive material to provide an adhesive bond that retains the stent to the catheter during vascular delivery, wherein the stent is released from the balloon following inflation and deflation of the balloon at a treatment site.

TECHNICAL FIELD

This invention relates generally to biomedical devices that are used fortreating vascular conditions. More specifically, the invention relatesto using an adhesive to improve retention of a stent to a ballooncatheter.

BACKGROUND OF THE INVENTION

Stents are generally cylindrical-shaped devices that are radiallyexpandable to hold open a segment of a vessel or other anatomical lumenafter implantation into the body lumen.

Various types of stents are in use, including expandable andself-expanding stents. Expandable stents generally are conveyed to thearea to be treated on balloon catheters or other expandable devices. Forinsertion, the stent is positioned in a compressed configuration alongthe delivery device, for example crimped onto a balloon that is foldedor otherwise wrapped about a guide wire that is part of the deliverydevice. After the stent is positioned across the lesion, it is expandedby the delivery device, causing the length of the stent to contract andthe diameter to expand. For a self-expanding stent, commonly a sheath isretracted, allowing expansion of the stent.

Stents are used in conjunction with balloon catheters in a variety ofmedical therapeutic applications, including intravascular angioplasty.For example, a balloon catheter device is inflated during percutaneoustransluminal coronary angioplasty (PTCA) to dilate a stenotic bloodvessel. The stenosis may be the result of a lesion such as a plaque orthrombus. When inflated, the pressurized balloon exerts a compressiveforce on the lesion, thereby increasing the inner diameter of theaffected vessel. The increased interior vessel diameter facilitatesimproved blood flow. Soon after the procedure, however, a significantproportion of treated vessels restenose.

To prevent restenosis, a stent, constructed of a metal or polymer, isimplanted within the vessel to maintain lumen size. The stent acts as ascaffold to support the lumen in an open position. Configurations ofstents include a cylindrical tube defined by a mesh, interconnectedstents, or like segments. Exemplary stents are disclosed in U.S. Pat.No. 5,292,331 to Boneau, U.S. Pat. No. 6,090,127 to Globerman, U.S. Pat.No. 5,133,732 to Wiktor, U.S. Pat. No. 4,739,762 to Palmaz, and U.S.Pat. No. 5,421,955 to Lau.

For a stent to provide the desired beneficial effect, it must bedelivered to precisely the correct position within a vessel.Disadvantages of some prior art stent delivery systems includedifficulty maintaining the stent on the delivery catheter whileadvancing the stent to and through the target treatment site anddifficulty releasing the stent once it is in place within the vessel.

Therefore, it would be desirable to provide a method and system forretaining a stent to a catheter for delivery and deployment of the stentin a vessel that overcomes the aforementioned and other disadvantages.

SUMMARY OF THE INVENTION

One aspect of the present invention is a method of manufacturing asystem for treating a vascular condition. A catheter including aninflatable balloon is provided. A stent is positioned over the balloon.An adhesive material is applied between an inner surface of the stentand an outer surface of the balloon. The adhesive material is heated toabove a melting point of the adhesive material. The adhesive material iscooled to below a melting point of the adhesive material to provide anadhesive bond that retains the stent to the catheter during vasculardelivery, wherein the stent is released from the balloon followinginflation and deflation of the balloon at a treatment site

Another aspect of the present invention is a system for treating avascular condition, comprising a catheter and a stent. The catheterincludes an inflatable balloon. The stent is removably coupled to theballoon with an adhesive material that has been heated to above amelting point of the adhesive material and cooled to below a meltingpoint of the adhesive material to provide an adhesive bond that retainsthe stent to the catheter during vascular delivery, wherein the stent isreleased from the balloon following inflation and deflation of theballoon at a treatment site

The aforementioned and other features and advantages of the inventionwill become further apparent from the following detailed description ofthe presently preferred embodiments, read in conjunction with theaccompanying drawings. The detailed description and drawings are merelyillustrative of the invention rather than limiting, the scope of theinvention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one embodiment of a system for treating avascular condition, in accordance with the present invention;

FIG. 2 is a flow diagram of one embodiment of a method of manufacturinga stent-graft assembly, in accordance with the present invention; and

FIG. 3 is a flow diagram of another embodiment of a method ofmanufacturing a system for treating a vascular condition, in accordancewith the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

One aspect of the present invention is a system for treating a vascularcondition. One embodiment of the system, in accordance with the presentinvention, is illustrated in FIG. 1 at 100. System 100 comprises acatheter 110, which includes an inflatable balloon 120, and a stent 130that is releasably coupled to balloon 120 with an adhesive material 140.

Catheter 110 may be any catheter known in the art that is appropriatefor delivering a stent to a lesion site, for example a percutaneoustransluminal coronary angioplasty (PTCA) balloon catheter. Inflatableballoon 120, which expands the stent once it has been delivered, may bemade of a suitable material such as polyethylene, polyethyleneterephthalate (PET), or from nylon or the like. The length and diameterof balloon 120 may be selected based on the dimensions of the stentbeing delivered.

Stent 130 is releasably coupled to balloon 120, and thereby to catheter110, with an adhesive material 140. Stent 130 may be made of a widevariety of medical implantable materials, including, but not limited to,stainless steel, nitinol, tantalum, ceramic, nickel, titanium, aluminum,polymeric materials, MP35N, stainless steel, titanium ASTM F63-83 Grade1, niobium, high carat gold K 19–22, and combinations of the above. Thestent may be formed with openings in its walls, such as spaces betweenportions of the wire in the case of a wire coil stent or holes in thecase of a tubular stent.

Adhesive material 140 is a biocompatible material having a melting pointbelow that of the balloon material, for example below approximately onehundred sixty-five degrees Fahrenheit (165° F.). One such material ispoly(ethylene oxide), which has a melting point between one hundredforty degrees Fahrenheit (140° F.) and one hundred sixty degreesFahrenheit (160° F.).

To create the present system, adhesive material 140 has been heated toabove its melting point and then cooled such that it forms weak adhesionpoints at the stent-balloon interface and, thus, a weak bond betweenstent 130 and balloon 120. The adhesive may, for example, have beenheated at a temperature of approximately one hundred sixty-five degreesFahrenheit (165° F.) for a time duration of approximately three minutesand then cooled to room temperature. The bond is strong enough to retainthe stent to the balloon during vascular delivery, while still beingweak enough to allow the stent to be released following inflation anddeflation of the balloon at a treatment site.

Another aspect of the present invention is a method of manufacturing asystem for treating a vascular condition. FIG. 2 shows a flow diagram ofone embodiment in accordance with the present invention at 200.

In this embodiment, a catheter is provided, the catheter including aninflatable balloon (Block 205). The catheter may be any catheter knownin the art that is appropriate for delivering a stent to a lesion siteidentified for treatment, for example a percutaneous transluminalcoronary angioplasty (PTCA) balloon catheter. The balloon may be madefrom a suitable material such as polyethylene, polyethyleneterephthalate (PET), or from nylon or the like. The length and diameterof the balloon may be selected based on the dimensions of the stentbeing delivered.

The balloon is folded or otherwise manipulated or treated to minimizeits profile (Block 210). A stent is positioned over the balloon by, forexample, slipping the stent over the folded balloon (Block 215). Asheath made of a material such as polytetrafluoroethylene (PTFE) or thelike is then positioned over the stent (Block 220), thereby enclosingboth the stent and the balloon.

An adhesive material is dispersed throughout a fluid (Block 225). Theadhesive material may comprise a biocompatible material having a meltingpoint below that of the balloon material, for example belowapproximately one hundred sixty-five degrees Fahrenheit (165° F.). Onesuch material is poly(ethylene oxide), which has a melting point betweenone hundred forty degrees Fahrenheit (140° F.) and one hundred sixtydegrees Fahrenheit (160° F.). The poly(ethylene oxide) may be dispersedin a fluid such as water to form a dilute solution. For example, onegram (1 g) of poly(ethylene oxide) may be dispersed in one hundred cubiccentimeters (100 cc) of water.

The adhesive material is applied between the inner surface of the stentand the outer surface of the balloon by introducing the adhesivematerial within the sheath (Block 230). This may be accomplished by, forexample, injecting a dilute solution of poly(ethylene oxide) within aPTFE sheath such that it flows between the inner surface of the stentand the outer surface of the balloon. Where the stent is formed withopenings in its walls, the sheath may aid both in directing the adhesivematerial between the stent and the balloon and in containing thematerial so it remains in place during the following steps.

The stent is then crimped onto the balloon (Block 235). The sheath mayadditionally provide protection for the stent during the crimpingprocess, reducing the risk of damage to the stent.

The balloon is pressurized with an inflation pressure of, for example,approximately seventy pounds per square inch (70 PSI), therebymaintaining the balloon in a partially inflated configuration during thefollowing heating and cooling steps (Block 240). Partially inflating theballoon provides good contact between the balloon and the stent and maycause the balloon to protrude through openings formed in the wall of thestent or at either end of the stent, improving stent retention. Theinterior diameter of the sheath may aid in defining the shape and sizeof any balloon protrusions, which may be permanently set by thefollowing heating and cooling steps.

The adhesive material is heated to above its melting point (Block 245).This may be accomplished by, for example, heating the assembly describedabove in a heat set block at a temperature of approximately one hundredsixty-five degrees Fahrenheit (165° F.) for approximately three minutes.

The adhesive material is then cooled to below its melting point, forexample by removing the assembly from the heat set block and allowing itto cool at room temperature (Block 250). Once the assembly has cooled,the inflation pressure is discontinued (Block 255), and the sheath isremoved from the assembly (Block 260). Alternatively, the sheath may beleft on the assembly for protection during shipping or storage.

Upon cooling, the adhesive material forms weak adhesion points at thestent-balloon interface and, thus, a weak bond between the stent and theballoon. This bond retains the stent to the balloon during vasculardelivery, while still allowing the stent to be released followinginflation and deflation of the balloon at a treatment site. Maintainingthe balloon in a partially expanded configuration during the heating andcooling steps may contribute to the adhesive bond formed between thestent and balloon.

FIG. 3 shows a flow diagram of another embodiment of a method ofmanufacturing a system for treating a vascular condition, in accordancewith the present invention at 300.

In this embodiment, a catheter is provided, the catheter including aninflatable balloon (Block 305). The catheter may be any catheter knownin the art that is appropriate for delivering a stent to a lesion siteidentified for treatment, for example a percutaneous transluminalcoronary angioplasty (PTCA) balloon catheter. The balloon may be madefrom a suitable material such as polyethylene, polyethyleneterephthalate (PET), or from nylon or the like. The length and diameterof the balloon may be selected based on the dimensions of the stentbeing delivered.

A stent is positioned over the balloon by, for example, slipping thestent over the balloon (Block 310). An adhesive material is appliedbetween an inner surface of the stent and an outer surface of theballoon (Block 315). The adhesive material may comprise a biocompatiblematerial having a melting point below that of the balloon material, forexample below approximately one hundred sixty-five degrees Fahrenheit(165° F.). One such material is poly(ethylene oxide), which has amelting point between one hundred forty degrees Fahrenheit (140° F.) andone hundred sixty degrees Fahrenheit (160° F.). The adhesive materialmay be applied by methods including, but not limited to, injecting,spraying, blowing, dipping, and the like.

The adhesive material is heated to above its melting point (Block 320).This may be accomplished by, for example, heating the system to atemperature of approximately one hundred sixty-five degrees Fahrenheit(165° F.) in a heat set block. The system is then cooled to below themelting point of the adhesive material by, for example, allowing it tocool at room temperature (Block 325).

Upon cooling, the adhesive material forms weak adhesion points at thestent-balloon interface and, thus, a weak bond between the stent and theballoon. This bond retains the stent to the balloon during vasculardelivery, while still allowing the stent to be released followinginflation and deflation of the balloon at a treatment site.

While the embodiments of the invention disclosed herein are presentlyconsidered to be preferred, various changes and modifications can bemade without departing from the spirit and scope of the invention. Thescope of the invention is indicated in the appended claims, and allchanges and modifications that come within the meaning and range ofequivalents are intended to be embraced therein.

1. A method of manufacturing a system for treating a vascular condition;comprising: providing a catheter, the catheter including an inflatableballoon; positioning a stent over the balloon; positioning a sheath overthe stent; applying an adhesive material between an inner surface of thestent and an outer surface of the balloon, the adhesive having a meltingpoint of at least one hundred forty degrees Fahrenheit (140° F.);heating the adhesive material to above the melting point of the adhesivematerial; cooling the adhesive material to below the melting point ofthe adhesive material to provide an adhesive bond that retains the stentto the catheter during vascular delivery, wherein the stent is releasedfrom the balloon following inflation and deflation of the balloon at atreatment site; and removing the sheath after cooling the adhesivematerial.
 2. The method of claim 1 wherein the sheath is formed withopenings in its walls.
 3. The method of claim 1 wherein the adhesivematerial comprises a biocompatible material having a melting pointbetween one hundred forty degrees Fahrenheit (140° F.) and one hundredsixty-file degrees Fahrenheit (165° F.).
 4. The method of claim 1wherein the adhesive material comprises poly(ethylene oxide).
 5. Themethod of claim 1 further comprising: minimizing the balloon profileprior to positioning the stent over the balloon.
 6. The method of claim1 further comprising: dispersing the adhesive material throughout afluid prior to application of the adhesive material.
 7. A method ofmanufacturing a system for treating a vascular condition; comprising:providing a catheter, the catheter including an inflatable balloon;positioning a stent over the balloon; positioning a sheath over thestent; dispersing an adhesive material throughout a fluid prior toapplication of the adhesive material applying the adhesive materialbetween an inner surface of the stent and an outer surface of theballoon, wherein approximately one gram (1 g) of adhesive material isdispersed throughout approximately one hundred cubic centimeters (100cc) of fluid; heating the adhesive material to above the melting pointof the adhesive material; cooling the adhesive material to below themelting point of the adhesive material to provide an adhesive bond thatretains the stent to the catheter during vascular delivery, wherein thestent is released from the balloon following inflation and deflation ofthe balloon at a treatment site; and removing the sheath after coolingthe adhesive material.
 8. The method of claim 1 wherein applying anadhesive material between an inner surface of the stent and an outersurface of the balloon comprises introducing the adhesive materialwithin the sheath such that the adhesive material flows between theinner surface of the stent and the outer surface of the balloon.
 9. Themethod of claim 1 further comprising: crimping the stent onto theballoon prior to heating the adhesive material.
 10. The method of claim1 further comprising: maintaining the balloon in a partially inflatedconfiguration while heating and cooling the adhesive material.
 11. Amethod of manufacturing a system for treating a vascular condition;comprising: providing a catheter, the catheter including an inflatableballoon; positioning a stent over the balloon; positioning a sheath overthe stent; applying an adhesive material between an inner surface of thestent and an outer surface of the balloon; heating the adhesive materialto a temperature of approximately one hundred sixty-five degreesFahrenheit (165° F.); cooling the adhesive material to below the meltingpoint of the adhesive material to provide an adhesive bond that retainsthe stent to the catheter during vascular delivery, wherein the stent isreleased from the balloon following inflation and deflation of theballoon at a treatment site; and removing the sheath after cooling theadhesive material.
 12. A method of manufacturing a system for treating avascular condition; comprising: providing a catheter, the catheterincluding an inflatable balloon; positioning a stent over the balloon;positioning a sheath over the stent; applying an adhesive materialbetween an inner surface of the stent and an outer surface of theballoon; heating the adhesive material to above a melting point of theadhesive material wherein the adhesive material is heated for a timeduration of approximately three minutes; cooling the adhesive materialto below the melting point of the adhesive material to provide anadhesive bond that retains the stent to the catheter during vasculardelivery, wherein the stent is released from the balloon followinginflation and deflation of the balloon at a treatment site; and removingthe sheath after cooling the adhesive material.
 13. The system of claim12 wherein the adhesive material comprises poly(ethylene oxide).
 14. Amethod of manufacturing a system for treating a vascular condition,comprising: providing a catheter, the catheter including an inflatableballoon; positioning a stent over the balloon; dispersing approximatelyone gram (1 g) of an adhesive material throughout approximately onehundred cubic centimeters (100 cc) of fluid; applying the dispersedadhesive material between an inner surface of the stent and an outersurface of the balloon; heating the adhesive material to above a meltingpoint of the adhesive material; and cooling the adhesive material tobelow a melting point of the adhesive material to provide an adhesivebond that retains the stent to the catheter during vascular delivery,wherein the stent is released from the balloon following inflation anddeflation of the balloon at a treatment site.
 15. The method of claim 14wherein the adhesive material comprises a biocompatible material havinga melting point below approximately one hundred sixty-five degreesFahrenheit (165° F.).
 16. The method of claim 14 wherein the adhesivematerial comprises poly(ethylene oxide).
 17. The method of claim 14further comprising: maintaining the balloon in a partially inflatedconfiguration while heating and cooling the adhesive material.
 18. Themethod of claim 14 wherein the adhesive material is heated at atemperature of approximately one hundred sixty-five degrees Fahrenheit(165° F.).
 19. A method of manufacturing a system for treating avascular condition, comprising: providing a catheter, the catheterincluding an inflatable balloon; positioning a stent over the balloon;applying an adhesive material between an inner surface of the stent andan outer surface of the balloon; heating the adhesive material at atemperature of approximately one hundred sixty-five degrees Fahrenheit(165° F.); and cooling the adhesive material to below a melting point ofthe adhesive material to provide an adhesive bond that retains the stentto the catheter during vascular delivery, wherein the stent is releasedfrom the balloon following inflation and deflation of the balloon at atreatment site.
 20. A method of manufacturing a system for treating avascular condition, comprising: providing a catheter, the catheterincluding an inflatable balloon; positioning a stent over the balloon;applying an adhesive material between an inner surface of the stent andan outer surface of the balloon; heating the adhesive material to abovea melting point of the adhesive material for a time duration ofapproximately three minutes; and cooling the adhesive material to belowa melting point of the adhesive material to provide an adhesive bondthat retains the stent to the catheter during vascular delivery, whereinthe stent is released from the balloon following inflation and deflationof the balloon at a treatment site.